I run a small fantasy site and had a question about this very trade (I wasnt given the guys full team however) Here was my answer and a few extra points specific to your roster;
I wouldn't do it for the following Reasons;
1.Maintain your rb1 advantage over other teams in your league. In a season void of many true 20-30 touch backs, you are sitting pretty with three such players in your starting lineup. Even average production from the trio combined with the ultimate QB1 in Brady, should give you a solid cushion when playing most if not all teams in your league. Protect and love this cushion, it will lead your squad to great places.
2.Injury concerns of your top two backs;
a. sjax...he will most likely miss time with another injury considering Bradford is going to be less than 100% for the forseeable future with that high ankle sprain allowing defenses to key on SJ even more in coming weeks, and as we all know he does not take kindly a heavy beating! Even when/if Brad is back, the team is still going to be down by large amounts all yr bc the defense is awful, limiting SJ's carries.
b. Turner is a good bet to break down at some point as well, nearly every back that led the nfl in attempts one season has broken down the next. To further this point, Turner actually continued that trend in 09 as he missed 6 games after leading the league in carries in 08.
-While the probability of both missing extended time is low, keeping Wells will help you cope with any injuries to the two.
3. Take advantage of the 2 wr format- You already have at least 1 mid-range wr on your roster in either Holmes/Rice. One, quite possibly both, will consistently preform as the season progresses. The second starter could be had off waivers with some luck if Harvin/Branch remain up and down. Again, you are sitting in the perfect position this season as you hold the most elusive commodity, rb1's, and need the most readily available position in a pass happy NFL.
-Your team is a few minor pieces away from being great, so focus on small additions such as steve breaston or greg Little on the free agent wire this week.